Examples with DJBHashFunction org.eclipse.ui.internal.texteditor.quickdiff.compare.equivalence.DJBHashFunction used on opensource projects

Example 1 with DJBHashFunction

use of org.eclipse.ui.internal.texteditor.quickdiff.compare.equivalence.DJBHashFunction in project eclipse.platform.text by eclipse.

the class DocumentLineDiffer method initialize.

/**
 * (Re-)initializes the differ using the current reference and <code>DiffInitializer</code>.
 *
 * @since 3.2 protected for testing reasons, package visible before
 */
protected synchronized void initialize() {
    // make new incoming changes go into the queue of stored events, plus signal we can't restore.
    fState = INITIALIZING;
    if (fRightDocument == null)
        return;
    // there is no point in receiving updates before the job we get a new copy of the document for diffing
    fIgnoreDocumentEvents = true;
    if (fLeftDocument != null) {
        fLeftDocument.removeDocumentListener(this);
        fLeftDocument = null;
        fLeftEquivalent = null;
    }
    // if there already is a job:
    // return if it has not started yet, cancel it if already running
    final Job oldJob = fInitializationJob;
    if (oldJob != null) {
        // don't chain up jobs if there is one waiting already.
        if (oldJob.getState() == Job.WAITING) {
            oldJob.wakeUp(INITIALIZE_DELAY);
            return;
        }
        oldJob.cancel();
    }
    fInitializationJob = new Job(QuickDiffMessages.quickdiff_initialize) {

        /*
			 * This is run in a different thread. As the documents might be synchronized, never ever
			 * access the documents in a synchronized section or expect deadlocks. See
			 * https://bugs.eclipse.org/bugs/show_bug.cgi?id=44692
			 */
        @Override
        public IStatus run(IProgressMonitor monitor) {
            // It will return relatively quickly as RangeDifferencer supports canceling
            if (oldJob != null)
                try {
                    oldJob.join();
                } catch (InterruptedException e) {
                    // will not happen as no one interrupts our thread
                    Assert.isTrue(false);
                }
            // 2:	get the reference document
            IQuickDiffReferenceProvider provider = fReferenceProvider;
            final IDocument left;
            try {
                left = provider == null ? null : provider.getReference(monitor);
            } catch (CoreException e) {
                synchronized (DocumentLineDiffer.this) {
                    if (isCanceled(monitor))
                        return Status.CANCEL_STATUS;
                    clearModel();
                    fireModelChanged();
                    return e.getStatus();
                }
            } catch (OperationCanceledException e) {
                return Status.CANCEL_STATUS;
            }
            // Getting our own copies of the documents for offline diffing.
            // 
            // We need to make sure that we do get all document modifications after
            // copying the documents as we want to re-inject them later on to become consistent.
            // fRightDocument, but not subject to change
            IDocument right = fRightDocument;
            // the copy of the actual (right) document
            IDocument actual = null;
            // the copy of the reference (left) document
            IDocument reference = null;
            synchronized (DocumentLineDiffer.this) {
                // 4: take an early exit if the documents are not valid
                if (left == null || right == null) {
                    if (isCanceled(monitor))
                        return Status.CANCEL_STATUS;
                    clearModel();
                    fireModelChanged();
                    return Status.OK_STATUS;
                }
                // set the reference document
                fLeftDocument = left;
                // start listening to document events.
                fIgnoreDocumentEvents = false;
            }
            // accessing the reference document from a different thread - reference providers need
            // to be able to deal with this.
            left.addDocumentListener(DocumentLineDiffer.this);
            // create the reference copy - note that any changes on the
            // reference will trigger re-initialization anyway
            reference = createCopy(left);
            if (reference == null)
                return Status.CANCEL_STATUS;
            // create the actual copy
            Object lock = null;
            if (right instanceof ISynchronizable)
                lock = ((ISynchronizable) right).getLockObject();
            if (lock != null) {
                // the document
                synchronized (lock) {
                    synchronized (DocumentLineDiffer.this) {
                        if (isCanceled(monitor))
                            return Status.CANCEL_STATUS;
                        fStoredEvents.clear();
                        actual = createUnprotectedCopy(right);
                    }
                }
            } else {
                // b) cannot lock the document
                // Now this is fun. The reference documents may be PartiallySynchronizedDocuments
                // which will result in a deadlock if they get changed externally before we get
                // our exclusive copies.
                // Here's what we do: we try over and over (without synchronization) to get copies
                // without interleaving modification. If there is a document change, we just repeat.
                int i = 0;
                do {
                    // this is an arbitrary emergency exit in case a referenced document goes nuts
                    if (i++ == 100)
                        return new Status(IStatus.ERROR, TextEditorPlugin.PLUGIN_ID, IStatus.OK, NLSUtility.format(QuickDiffMessages.quickdiff_error_getting_document_content, new Object[] { left.getClass(), right.getClass() }), null);
                    synchronized (DocumentLineDiffer.this) {
                        if (isCanceled(monitor))
                            return Status.CANCEL_STATUS;
                        fStoredEvents.clear();
                    }
                    // access documents non synchronized:
                    // get an exclusive copy of the actual document
                    actual = createCopy(right);
                    synchronized (DocumentLineDiffer.this) {
                        if (isCanceled(monitor))
                            return Status.CANCEL_STATUS;
                        if (fStoredEvents.size() == 0 && actual != null)
                            break;
                    }
                } while (true);
            }
            IHashFunction hash = new DJBHashFunction();
            DocumentEquivalenceClass leftEquivalent = new DocumentEquivalenceClass(reference, hash);
            fLeftEquivalent = leftEquivalent;
            IRangeComparator ref = new DocEquivalenceComparator(leftEquivalent, null);
            DocumentEquivalenceClass rightEquivalent = new DocumentEquivalenceClass(actual, hash);
            fRightEquivalent = rightEquivalent;
            IRangeComparator act = new DocEquivalenceComparator(rightEquivalent, null);
            ArrayList<QuickDiffRangeDifference> diffs = asQuickDiffRangeDifference(RangeDifferencer.findRanges(fRangeDiffFactory, monitor, ref, act));
            // re-inject stored events to get up to date.
            synchronized (DocumentLineDiffer.this) {
                if (isCanceled(monitor))
                    return Status.CANCEL_STATUS;
                // set the new differences so we can operate on them
                fDifferences = diffs;
            }
            // re-inject events accumulated in the meantime.
            try {
                do {
                    DocumentEvent event;
                    synchronized (DocumentLineDiffer.this) {
                        if (isCanceled(monitor))
                            return Status.CANCEL_STATUS;
                        if (fStoredEvents.isEmpty()) {
                            // we are back in sync with the life documents
                            fInitializationJob = null;
                            fState = SYNCHRONIZED;
                            fLastDifference = null;
                            // replace the private documents with the actual
                            leftEquivalent.setDocument(left);
                            rightEquivalent.setDocument(right);
                            break;
                        }
                        event = fStoredEvents.remove(0);
                    }
                    // access documents non synchronized:
                    IDocument copy = null;
                    if (event.fDocument == right)
                        copy = actual;
                    else if (event.fDocument == left)
                        copy = reference;
                    else
                        Assert.isTrue(false);
                    // copy the event to inject it into our diff copies
                    // don't modify the original event! See https://bugs.eclipse.org/bugs/show_bug.cgi?id=134227
                    event = new DocumentEvent(copy, event.fOffset, event.fLength, event.fText);
                    handleAboutToBeChanged(event);
                    // inject the event into our private copy
                    actual.replace(event.fOffset, event.fLength, event.fText);
                    handleChanged(event);
                } while (true);
            } catch (BadLocationException e) {
                left.removeDocumentListener(DocumentLineDiffer.this);
                clearModel();
                initialize();
                return Status.CANCEL_STATUS;
            }
            fireModelChanged();
            return Status.OK_STATUS;
        }

        private boolean isCanceled(IProgressMonitor monitor) {
            return fInitializationJob != this || monitor != null && monitor.isCanceled();
        }

        private void clearModel() {
            synchronized (DocumentLineDiffer.this) {
                fLeftDocument = null;
                fLeftEquivalent = null;
                fInitializationJob = null;
                fStoredEvents.clear();
                fLastDifference = null;
                fDifferences.clear();
            }
        }

        /**
         * Creates a copy of <code>document</code> and catches any
         * exceptions that may occur if the document is modified concurrently.
         * Only call this method in a synchronized block if the document is
         * an ISynchronizable and has been locked, as document.get() is called
         * and may result in a deadlock otherwise.
         *
         * @param document the document to create a copy of
         * @return a copy of the document, or <code>null</code> if an exception was thrown
         */
        private IDocument createCopy(IDocument document) {
            Assert.isNotNull(document);
            // this fixes https://bugs.eclipse.org/bugs/show_bug.cgi?id=56091
            try {
                return createUnprotectedCopy(document);
            } catch (NullPointerException e) {
            } catch (ArrayStoreException e) {
            } catch (IndexOutOfBoundsException e) {
            } catch (ConcurrentModificationException e) {
            } catch (NegativeArraySizeException e) {
            }
            return null;
        }

        private IDocument createUnprotectedCopy(IDocument document) {
            return new Document(document.get());
        }
    };
    fInitializationJob.setSystem(true);
    fInitializationJob.setPriority(Job.DECORATE);
    fInitializationJob.setProperty(IProgressConstants.NO_IMMEDIATE_ERROR_PROMPT_PROPERTY, Boolean.TRUE);
    fInitializationJob.schedule(INITIALIZE_DELAY);
}